JP5690627B2 - Polymer particles and uses thereof - Google Patents

Description

  The present invention relates to polymer particles, an external additive for an electrophotographic toner using the same, and a carrier coat additive.

In electrophotography and electrostatic recording, an electrostatic charge image is formed on a photosensitive member or electrostatic recording member, and an electrostatic charge image is formed by a magnetic brush development method or a cascade development method using an electrophotographic toner or carrier. Is developed to form a toner image, and the toner image is transferred and fixed on a copy paper or the like to form a copy.
For example, JP-A-60-186854 (Patent Document 1) and JP-A-59-104664 (Patent Document 2) disclose polymer particles (hereinafter referred to as “external additive for toner”) in electrophotographic toner. In addition, a technique is disclosed in which a coating layer composed of polymer particles (hereinafter referred to as “carrier coat additive”) is formed on a carrier to improve the performance thereof.

The polymer particles used in such an application example may be easily fused to each other by mechanical external force or heat if the hardness is too low, and contained in the toner if the solvent resistance is too low. There is a problem that polymer particles are dissolved by a charge control agent or paraffin.
Therefore, as a method for solving these problems, for example, Japanese Patent Application Laid-Open No. 7-104512 (Patent Document 3) is formed by seed polymerization of a polyfunctional monomer using hydrophobic polymer particles as seed particles. Highly crosslinked polymer fine particles are proposed, and Japanese Patent Application Laid-Open No. 2001-163985 (Patent Document 4) proposes crosslinkable polymer fine particles having a gel fraction of 25% by weight or more.

JP-A-60-186854 JP 59-104664 A Japanese Patent Laid-Open No. 7-104512 JP 2001-163985 A

  However, although the crosslinkable polymer particles of the prior art have hardness and solvent resistance, they do not have thermal characteristics suitable for adhesion and fusing properties. For example, when cross-linkable polymer particles are used as an external additive for an electrophotographic toner, they are easily detached or unevenly distributed from the toner by stirring, and it is difficult to impart sufficient fluidity and chargeability to the toner. When used as an additive, there is a problem that the coat layer is easily peeled off from the carrier core.

  Therefore, the present invention provides polymer particles having thermal characteristics that can be appropriately fused by mechanical external force and heat, and particularly suitable for external additives for electrophotographic toners and carrier coat additives used for electrostatic charging phenomena. It is an object to provide coalesced particles.

  The inventors of the present invention have conducted extensive research to solve the above problems, and as a result, polymer particles having a specific thermal characteristic while having a high gel fraction are used as external additives for electrophotographic toners. When used as a carrier coat additive, it can be appropriately melted by mechanical external force and heat in the external addition process to suppress falling off and uneven distribution from the toner. It has been found that it is possible to suppress the detachment of the coat layer from the carrier core by bonding with other additives, and the present invention has been completed.

Thus, according to the present invention, (meth) acrylic acid ester-based monomer derived from a polymerizable monomer containing 50 to 97% by weight and an asymmetric polyvinyl monomer having two or more vinyl groups having different reactivity. Composed of a polymer of
The (meth) acrylate monomer is methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) T-butyl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate and At least one selected from stearyl (meth) acrylate,
The asymmetric polyvinyl monomer is allyl (meth) acrylate, and has an average particle size of 0.05 to 0.5 μm, a gel fraction of 60% or more, and 160 of 3 × 10 ⁴ to 2 × 10 ⁶ Pa or less. Polymer particles characterized by having a storage modulus G ′ at 0 ° C. are provided.

  In addition, according to the present invention, there are provided an external additive for electrophotographic toner and a carrier coat additive containing the above polymer particles.

According to the present invention, polymer particles having thermal characteristics that can be appropriately fused by a mechanical external force and heat, particularly suitable for external additives for electrophotographic toners and carrier coat additives used for electrostatic charging phenomenon. Combined particles can be provided.
That is, since the polymer particles of the present invention have specific thermal characteristics while having a high gel fraction, they can be suitably used as an external additive for toner or a carrier coat additive.

The polymer particles of the present invention are derived from a polymerizable monomer containing 50 to 97% by weight of a (meth) acrylic acid ester monomer and 3 to 50% by weight of an asymmetric polyvinyl monomer having two or more vinyl groups having different reactivity. It is composed of a polymer and has an average particle diameter of 0.05 to 1.0 μm, a gel fraction of 60% or more, and a storage elastic modulus G ′ at 160 ° C. of 3 × 10 ⁴ to 2 × 10 ⁶ Pa or less. It is characterized by.
In the present invention, “(meth) acryl” means acrylic or methacrylic.

The polymer particles of the present invention have an average particle size of 0.05 to 1.0 μm.
If the average particle size is less than 0.05 μm, a large amount of dispersion stabilizer must be used during the polymerization, and the hygroscopicity of the polymer particles becomes high, which is used as an external additive for electrophotographic toners and a carrier coat additive. In some cases, the chargeability of the toner or carrier may be reduced. On the other hand, when the average particle size exceeds 1.0 μm, the fluidity of the toner may be deteriorated when used as an external additive for electrophotographic toner. When used as a carrier coat additive, It may not be possible to coat uniformly. A more preferable average particle diameter is 0.05 to 0.5 μm. In addition, the measuring method of an average particle diameter is demonstrated in an Example.

The polymer particles of the present invention have a gel fraction of 60% or more.
“Gel fraction” means a weight ratio calculated from the weight of a dissolved product by putting polymer particles in an organic solvent in which the polymer particles can be dissolved. In the present invention, the gel fraction with respect to toluene, ie, organic It means the weight ratio calculated from the weight of the dissolved product when toluene is used as the solvent. In addition, the measuring method of a gel fraction is demonstrated in an Example.
When the gel fraction is less than 60%, the hardness of the polymer particles becomes insufficient, and the fine particles may be easily fused with each other by mechanical external force or heat, and against the charge control agent or paraffin contained in the toner. The solvent resistance may not be satisfied. The upper limit of the gel fraction is not particularly limited, and the preferred gel fraction is 65% or more, and particularly preferably 70% or more.

Furthermore, the polymer particles of the present invention have a storage elastic modulus G ′ at 160 ° C. of 3 × 10 ⁴ to 2 × 10 ⁶ Pa or less.
“Storage elastic modulus” is an index indicating the elasticity of polymer particles. Using a viscoelasticity measuring device, the strain of polymer particles under the conditions of 1% strain, frequency 1 Hz, temperature drop measurement from 230 ° C. to 90 ° C. It means the value G ′ of storage elastic modulus at 160 ° C. obtained by melt viscoelasticity measurement. In addition, the measuring method of storage elastic modulus G 'is demonstrated in an Example.

When the storage elastic modulus at 160 ° C. is less than 3 × 10 ⁴ Pa, the mechanical strength becomes poor when used as an external additive for an electrophotographic toner, and the polymer particles are greatly deformed at the time of external addition. In some cases, fluidity cannot be imparted, and when used as a carrier coat additive, mechanical strength is poor, and peeling or chipping is likely to occur. On the other hand, when the storage elastic modulus at 160 ° C. exceeds 2 × 10 ⁶ Pa, when it is used as an external additive for electrophotographic toner, it is desorbed or unevenly distributed from the toner by stirring, and the toner has sufficient fluidity and charge. When used as a carrier coat additive, adhesion to the carrier core and other components of the coat layer may be insufficient, and the coat layer may be easily peeled off from the carrier core. There is. A more preferable storage elastic modulus is 8 × 10 ^{4 to} 1.5 × 10 ⁶ Pa at 160 ° C.

The polymer particles of the present invention can be obtained by polymerizing a polymerizable monomer containing a (meth) acrylic acid ester monomer and an asymmetric polyvinyl monomer by a known method such as suspension polymerization, emulsion polymerization, or dispersion polymerization. . Among these, emulsion polymerization is particularly preferable in that the particle diameter can be easily controlled and charged polymer particles can be easily obtained.
Hereinafter, although the case of emulsion polymerization is demonstrated, this invention is not limited by this.
The polymer particles of the present invention are prepared by, for example, dispersing a polymerizable monomer mixture (a mixture of a (meth) acrylate monomer and an asymmetric polyvinyl monomer) in an aqueous medium containing a dispersion stabilizer, and adding a polymerization initiator. It can be produced by polymerizing under predetermined conditions.

(1) (meth) (meth) acrylic acid ester monomers used in the acrylate monomers present invention, for example, (meth) acrylate, (meth) acrylate, (meth) acrylate, propyl N-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, ( Examples include isodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, and stearyl (meth) acrylate. These may be used alone or in combination of two or more.

(2) Asymmetric polyvinyl monomer In the present invention, an asymmetric polyvinyl monomer having two or more vinyl groups having different reactivity (hereinafter, also simply referred to as “asymmetric polyvinyl monomer”) is used as a crosslinkable monomer.
“Two or more vinyl groups having different reactivities” means two or more vinyl groups having different reactivities during the polymerization reaction by bonding different substituents to the vinyl group. It is referred to as a “soluble polyvinyl monomer”. “Poly” means having two or more vinyl groups having different reactivities. For example, when there are three vinyl groups having different reactivity, it is sufficient that at least one vinyl group is different in reactivity from the other two vinyl groups.

  When polymer particles obtained by using a general crosslinkable monomer such as divinylbenzene or alkylene glycol dimethacrylate (alkylene having 2 to 4 carbon atoms) are polymerized under the condition of high gel fraction, It does not have specific thermal properties like the polymer particles of the invention. In contrast, the polymer particles of the present invention obtained using an asymmetric polyvinyl monomer as specified in the present invention have specific thermal characteristics even when polymerized under conditions that give a high gel fraction. , Have proper adhesiveness and fusion.

  Examples of the asymmetric polyvinyl monomer used in the present invention include allyl (meth) acrylate, 2- (2-vinyloxyethoxy) ethyl (meth) acrylate, and vinyl (meth) acrylate. These may be used alone or in combination of two or more. Among these, allyl (meth) acrylate is preferable from the viewpoint of polymerization stability.

The asymmetric polyvinyl monomer is 3 to 50% by weight, preferably 5 to 40% by weight, more preferably 5 to 30% by weight, based on the total amount of monomers including the (meth) acrylic acid ester monomer. is there.
When the amount of the asymmetric polyvinyl monomer is less than 3% by weight, the gel fraction of the polymer particles obtained may be excessively lowered. On the other hand, if the asymmetric polyvinyl monomer exceeds 50% by weight, it may not have specific thermal characteristics.
Therefore, the proportion of the (meth) acrylic acid ester monomer and the asymmetric polyvinyl monomer is 50 to 97% by weight and 3 to 50% by weight, preferably 60 to 95% by weight and 5 to 40% by weight, More preferably, they are 70-95 weight% and 5-30 weight%.

(3) Other additives The polymer particles of the present invention are within the range that does not impair the effects of the present invention, and if necessary, stabilizers, ultraviolet absorbers, pigments, dyes, antifoaming agents, thickeners, heat Stabilizers, leveling agents, lubricants, antistatic agents and the like may be included.

(4) Dispersion stabilizer Examples of the surfactant used in the emulsion polymerization of the polymer particles of the present invention include anionic surfactants, cationic surfactants, zwitterionic surfactants, and nonionic surfactants. A well-known surfactant is mentioned.

Examples of the anionic surfactant include non-reactive anionic surfactants such as alkylbenzene sulfonate, alkyl diphenyl ether sulfonate, dialkyl sulfosuccinate and monoalkyl sulfosuccinate, polyoxyethylene-1- ( And reactive anionic surfactants such as allyloxymethyl) alkyl ether sulfate ammonium salt, polyoxyethylene alkylpropenyl phenyl ether sulfate ammonium salt, and polyoxyalkylene alkenyl ether ammonium sulfate.
Examples of the cationic surfactant include cationic properties such as alkyltrimethylammonium salt, alkyltriethylammonium salt, dialkyldimethylammonium salt, dialkyldiethylammonium salt, and N-polyoxyalkylene-N, N, N-trialkylammonium salt. Surfactant etc. are mentioned.

Examples of the zwitterionic surfactant include lauryl dimethylamine oxide, phosphate ester salt, phosphite ester surfactant, and the like.
Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polysorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, oxyethylene -An oxypropylene block polymer etc. are mentioned.
These may be used alone or in combination of two or more.

Although the dispersion stabilizer differs depending on the type and the like, it is 0.01 with respect to 100 parts by weight of the total amount of the asymmetric polyvinyl monomer having two or more vinyl groups having different reactivity with the (meth) acrylic acid ester monomer. It is preferable to use -2.0 weight part.
If the amount of the dispersion stabilizer used is less than 0.01 parts by weight, the polymerization stability may be lowered during the polymerization, and particle aggregation and coalescence may occur during the polymerization. On the other hand, if the amount of the dispersion stabilizer used exceeds 2.0 parts by weight, sufficient fluidity may not be imparted to the toner. A more preferable amount of the dispersion stabilizer is 0.05 to 1.0 part by weight.

(5) Polymerization initiator The polymerization initiator used in the present invention is not particularly limited. For example, persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate; benzoyl peroxide, acetyl peroxide, methyl ethyl ketone peroxide Organic peroxides such as oxide, t-butyl peroxide, dicumyl peroxide; 2,2-azobis [2- (2-imidazolin-2-yl) propane] hydrogen dichloride, 2,2-azobis [2 -(2-Imidazolin-2-yl) propane] disulfate dihydrate, 2,2-azobis (2-amidinopropane) dihydrochloride, 2,2-azobis [N- (2-carboxyethyl) -2 -Methylpropionamidine] hydrate, 2,2-azobis {2- [1- (2-hydroxyethyl) -2-imidazoline-2 -Yl] propane} hydrogen dichloride, 2,2-azobis [2- (2-imidazolin-2-yl) propane], 2,2-azobis (1-imino-1-pyrrolidino-2-ethylpropane) dichloride Hydrogen, 2,2-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2-azobis [2-methyl-N- (2-hydroxy) Ethyl) propionamide], 2,2-azobis (N-hydroxyethylisobutyramide), 4,4-azobis (4-cyanopentanoic acid), azobisisobutyronitrile, azobis (2,4dimethylvaleronitrile), etc. Of the azo compounds.

In addition, as polymerization initiators, the above-mentioned polymerization initiators of persulfates and organic peroxides include sodium sulfooxylate formaldehyde, sodium hydrogen sulfite, ammonium hydrogen sulfite, sodium thiosulfate, ammonium thiosulfate, hydrogen peroxide, Examples also include redox initiators that are used in combination with reducing agents such as sodium hydroxymethanesulfinate, L-ascorbic acid and salts thereof, cuprous salts, and ferrous salts.
Said polymerization initiator may be used individually by 1 type, or may use 2 or more types together.
The polymerization initiator varies depending on the type thereof, but is 0.1% with respect to 100 parts by weight of the total amount of asymmetric polyvinyl monomers having two or more vinyl groups having different reactivity with the (meth) acrylic acid ester monomer. It is preferable to use ˜5 parts by weight. A more preferable use amount of the polymerization initiator is 0.3 to 3 parts by weight.

(6) Chain transfer agent A chain transfer agent may be added in emulsion polymerization.
The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, α-methylstyrene dimer, 2, Examples thereof include phenolic compounds such as 6-di-t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, and halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, and carbon tetrachloride. These may be used alone or in combination of two or more.
The chain transfer agent may be used in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the total amount of asymmetric polyvinyl monomers having two or more vinyl groups that are different in reactivity from the (meth) acrylic acid ester monomer. preferable. A more preferable amount of the chain transfer agent used is 0.3 to 3 parts by weight.

(7) Aqueous medium The ratio of the polymerizable monomer mixture to the aqueous medium is preferably in the range of 1:20 to 1: 2. When the ratio of the polymerizable monomer mixture falls below the above range, the productivity of the polymer particles may be lowered. On the other hand, when the ratio of the polymerizable monomer mixture exceeds the above range, the stability of the particles during the polymerization may be reduced, and an aggregate of polymer particles may be generated after the polymerization. More preferably, it is 1:15 to 1: 3.

(8) Polymerization conditions The polymerization temperature and polymerization time may be appropriately set depending on the monomer composition to be used, the type and amount of the polymerization initiator used, and are usually preferably 30 to 100 ° C and 2 to 10 hours.
At the time of polymerization, it is preferable to stir using a mechanical stirring device such as ultrasonic irradiation and / or a magnetic stirrer in order to ensure uniformity of polymerization and prevent coalescence of polymer particles. The stirring speed may be appropriately set depending on the type of apparatus to be used, the stirring ability, and the like. For example, when a reactor having a capacity of 5 L (liter) is used, it is preferably 100 to 500 rpm.

  Further, after polymerization, the polymer particles may be isolated (dehydrated) from the aqueous medium and dried using a known method. Examples of the drying method include a spray drying method using a spray dryer, a method of drying by adhering to a heated rotating drum using a drum dryer, a freeze drying method, and the like. Furthermore, it is preferable to pulverize the dried aggregates of polymer particles using a pulverizer or a pulverizer.

The external additive for an electrophotographic toner of the present invention is characterized by containing the polymer particles of the present invention.
The electrophotographic toner is usually used as an external additive for an electrophotographic toner to toner base particles obtained by melt-kneading a toner composition containing at least a binder resin, a colorant and a release agent, and then pulverizing and classifying the toner composition. It is produced by externally adding the polymer particles of the invention.
The external addition method is not particularly limited, and examples thereof include a method in which the toner base particles, the polymer particles of the present invention, and other additives as necessary are mixed with a mixer or the like.
The external additive for electrophotographic toner is usually externally added to control the fluidity and chargeability of the toner. Since the polymer particles of the present invention have specific thermal characteristics, they can be appropriately fused with the toner base particles by mechanical external force and heat in the external addition process, and can be prevented from falling off from the toner and being unevenly distributed. Therefore, stable fluidity and chargeability can be imparted to the electrophotographic toner.
The blending amount of the polymer particles of the present invention is usually 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the toner base particles.

The carrier coat additive of the present invention is characterized by containing the polymer particles of the present invention.
Toner for electrostatic charge development (two-component developer) is usually obtained by melting and kneading a toner composition containing at least a binder resin, a colorant, and a release agent, and then pulverizing and classifying the toner base particles. It is manufactured by adding a carrier such as.
As a carrier, a carrier in which a carrier core particle is coated with a coating layer made of a resin is currently widely used in order to control charging property and charging stability.
When the polymer particles of the present invention are used as a coating additive for coating a carrier, since the polymer particles have specific thermal characteristics, the carrier core and the coat layer can be more closely adhered to each other. Peeling and chipping of the coat layer can be suppressed.
The coating method is not particularly limited, and examples thereof include a method in which the carrier, the polymer particles of the present invention, and other additives as required are treated by the fluidized bed method described in Patent Document 2, for example.
The blending amount of the polymer particles of the present invention is usually 5 to 90 parts by weight, preferably 10 to 80 parts by weight with respect to 100 parts by weight of the carrier coat layer.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these.
First, a method for measuring and evaluating physical properties of polymer particles obtained in Examples and Comparative Examples and pseudo toner particles obtained using the polymer particles will be described.

(1) Average particle diameter In the present invention, “average particle diameter” means an average particle diameter measured using a method called a dynamic light scattering method or a photon correlation method. That is, at 25 ° C., an aqueous dispersion of polymer particles prepared at 0.1% by volume is irradiated with laser light, and the intensity of scattered light scattered from the polymer particles is measured with a time change in units of microseconds. The scattering intensity distribution resulting from the detected polymer particles is applied to a normal distribution, and the average particle diameter is calculated by a cumulant analysis method.
This average particle diameter can be easily measured with a measuring apparatus equipped with commercially available data analysis software, and can be automatically analyzed. In the present Example, it measured using the particle diameter measuring apparatus "Zetasizer nano ZS" by a Malvern company (Spectris Co., Ltd.).

(2) Solvent resistance (gel fraction)
In the present invention, the “gel fraction” means a weight ratio calculated from the weight of the dissolved product by introducing the polymer particles into an organic solvent in which the polymer particles can be dissolved. That is, about 0.1 g of dried polymer particles are precisely weighed, put into 10 ml of toluene, stirred with a stirrer bar for 30 minutes, and then allowed to stand for 15 hours. Next, after stirring again with a stir bar for 30 minutes, the toluene solution is centrifuged at 10,000 rpm for 30 minutes, and then the supernatant is evaporated to dryness on a hot plate at 100 ° C. Heat in a dryer at 105 ° C for 10 minutes, allow to cool in a desiccator, weigh the resulting dried product (polymer particles dissolved in an organic solvent), and calculate the gel fraction (wt%) according to the following formula: calculate.
Gel fraction (% by weight) = 100− (weight of dried product / weight of sample) × 100
The solvent resistance is evaluated according to the following criteria from the obtained gel fraction.
○: Gel fraction 60% or more (having excellent solvent resistance)
X: Gel fraction less than 60% (poor solvent resistance)

(3) Storage elastic modulus (thermal characteristics)
In the present invention, the “storage elastic modulus” is obtained by measuring the melt viscoelasticity of polymer particles under the conditions of a 1% strain, a frequency of 1 Hz, and a temperature drop measurement from 230 ° C. to 90 ° C. using a viscoelasticity measuring device. It means the storage elastic modulus value G ′ at 160 ° C. That is, polymer particles were preliminarily heat-molded at 230 ° C. to prepare a test piece having a diameter of 8 mm (± 1 mm) and a thickness of 1.0 mm (± 0.1 mm), and a viscoelasticity measuring device (manufactured by Anton Paar; MCR-301). The melt viscoelasticity is measured under the following conditions.
Measurement mode: Temperature sweep Gap length: 1.0 mm (± 0.1 mm)
Frequency: 1Hz
Plate: Parallel plate φ8mm
Measurement temperature: 230 ° C to 90 ° C
Temperature drop rate: 2 ° C / min
From the above measurement, a storage elastic modulus value G ′ at 160 ° C. is obtained.

(4) Screening rate (fluidity)
In the present invention, the “screening rate” means a weight ratio of the pseudo toner obtained by externally adding polymer particles to a toner binder resin and passing through a screen having a specific opening. That is, (a) a pseudo toner is prepared and (b) is measured as follows.

(A) Preparation of pseudo toner In a 5 L autoclave, 26 parts by weight of magnesium pyrophosphate was dispersed in 2600 parts by weight of water, 0.13 parts by weight of sodium nitrite, a phosphorus surfactant (manufactured by Toho Chemical Industry Co., Ltd.) , Product name: Phosphanol LO-529) 1.3 parts by weight are dissolved. Further, a mixed solution of 910 parts by weight of styrene and 390 parts by weight of butyl methacrylate in which 10.4 parts by weight of azobisisobutyronitrile and 3.9 parts by weight of t-butylperoxy-2-ethylhexanoate are dissolved. And emulsifying at a rotational speed of 4000 rpm using a high-speed emulsification / dispersing machine (special machine industry Co., Ltd. (currently Primix Co., Ltd., model: TK HOMOMIXER MARKII)), then a nanomizer system (nanomizer) A dispersion is obtained by processing at a pressure of 0.5 MPa using a model LA-33 manufactured by Co., Ltd.

  The obtained dispersion is heated to 60 ° C. while stirring at a rotation speed of 450 rpm, and maintained at that temperature for 6 hours. Thereafter, 100 parts by weight of water in which 1.3 parts by weight of sulfamic acid and 2.6 parts by weight of sodium dodecylbenzenesulfonate were dissolved was added, heated to 110 ° C. with stirring, and further maintained for 1 hour to polymerize the monomer. Let Thereafter, it is cooled to room temperature, dehydrated and dried to obtain a toner binder resin. In this example, 1150 g of a binder resin for toner having an average particle size of 10 μm was obtained.

  A mixture of 15 g of the obtained binder resin for toner and 0.45 g of polymer particles was mixed for 5 seconds using a mill mixer (manufactured by Panasonic Corporation, product name: Fiber Mixer MX-X57-Y), and then 1 Let stand for a minute. The mixing process for 5 seconds and the standing for 1 minute are repeated again, and this operation is performed a total of 5 times to obtain a pseudo toner.

(B) Measurement of sieve passing rate 2 g of the obtained pseudo toner was placed on a metal sieve having an opening of 45 μm, and this sieve was installed in a powder property evaluation apparatus (manufactured by Hosokawa Micron Corporation, model: Powder Tester PX-X). Then, a rheostat voltage of 7.2 V is applied and the sieve is vibrated for 93 seconds. After the vibration is finished, the weight of the residue on the sieve is measured, and the sieve passing rate Pb (% by weight) is calculated by the following formula.
Sieve passing rate Pb (% by weight) = 100− (weight of residue / 2) × 100
The fluidity is evaluated from the obtained sieve passage rate according to the following criteria.
○: Screening rate 95% or more (excellent fluidity can be imparted)
×: Screening rate less than 95% (poor fluidity)

Example 1
Ion exchange in which 4 parts by weight of stearyltrimethylammonium chloride (manufactured by Kao Corporation, product name: Cotamine 86W) as a surfactant is deoxygenated in a 5 L autoclave equipped with a stirrer, reflux condenser and thermometer. Dissolve in 3200 parts by weight of water, and further supply 760 parts by weight of methyl methacrylate (MMA) and 40 parts by weight of allyl methacrylate (AMA). ), Type: TK HOMOMIXER MARK II), and a dispersion was prepared.
In the resulting dispersion, 2,2-azobis (2-amidinopropane) dihydrochloride as a polymerization initiator (10 hour half-life temperature: 56 ° C., manufactured by Wako Pure Chemical Industries, Ltd., product name: V-50) 4 parts by weight were added, and the dispersion was heated to 70 ° C. with stirring, and held at that temperature for 3 hours to carry out emulsion polymerization. Then, it cooled to room temperature, it was made to dry with spray drying, and the obtained polymer lump was crushed with the jet mill, and the polymer particle 640g was obtained.
The obtained polymer particles have an average particle size of 0.09 μm, a gel fraction of 91.9%, a storage elastic modulus of 4.9 × 10 ⁵ , and an external additive for electrophotographic toner used for electrostatic charging phenomenon. In addition, it was suitably used as a carrier coat additive.

(Example 2)
640 g of polymer particles were obtained in the same manner as in Example 1 except that 640 parts by weight of methyl methacrylate and 160 parts by weight of allyl methacrylate were used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate. It was.
The obtained polymer particles have an average particle size of 0.09 μm, a gel fraction of 99.4%, a storage elastic modulus of 7.0 × 10 ⁵ , and an external additive for electrophotographic toner used for electrostatic charging phenomenon. In addition, it was suitably used as a carrier coat additive.

(Example 3)
Example 1 is used except that instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate, 320 parts by weight of methyl methacrylate, 320 parts by weight of isobutyl methacrylate (IBMA) and 160 parts by weight of allyl methacrylate are used. Similarly, 640 g of polymer particles were obtained.
The obtained polymer particles have an average particle size of 0.09 μm, a gel fraction of 86.4%, a storage elastic modulus of 5.1 × 10 ⁵ , and an external additive for electrophotographic toner used for electrostatic charging phenomenon. In addition, it was suitably used as a carrier coat additive.

Example 4
Example, except that 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate were used, 320 parts by weight of isobutyl methacrylate, 320 parts by weight of Tashary butyl methacrylate (TBMA) and 160 parts by weight of allyl methacrylate were used. In the same manner as in Example 1, 640 g of polymer particles were obtained.
The obtained polymer particles have an average particle diameter of 0.10 μm, a gel fraction of 80.9%, a storage elastic modulus of 4.2 × 10 ⁵ , and an external additive for electrophotographic toner used for electrostatic charging phenomenon. In addition, it was suitably used as a carrier coat additive.

(Example 5)
Polymer particles in the same manner as in Example 1, except that 640 parts by weight of cyclohexyl methacrylate (CHMA) and 160 parts by weight of allyl methacrylate were used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate. 640 g was obtained.
The obtained polymer particles have an average particle size of 0.10 μm, a gel fraction of 98.2%, and a storage elastic modulus of 3.8 × 10 ⁵ , and are external additives for electrophotographic toner used for electrostatic charging phenomenon. In addition, it was suitably used as a carrier coat additive.

(Comparative Example 1)
640 g of polymer particles were obtained in the same manner as in Example 1 except that 800 parts by weight of methyl methacrylate was used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate.
The obtained polymer particles had an average particle size of 0.09 μm, a gel fraction of 0.1%, and a storage elastic modulus of 3.8 × 10 ⁵ . The polymer particles have a low gel fraction and poor solvent resistance, and are unsuitable as external additives for electrophotographic toners and carrier coat additives used for electrostatic charging phenomenon.

(Comparative Example 2)
640 g of polymer particles were obtained in the same manner as in Example 1 except that 792 parts by weight of methyl methacrylate and 8 parts by weight of allyl methacrylate were used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate. It was.
The obtained polymer particles had an average particle size of 0.09 μm, a gel fraction of 41.5%, and a storage elastic modulus of 4.1 × 10 ⁵ . The polymer particles have a low gel fraction and poor solvent resistance, and are unsuitable as external additives for electrophotographic toners and carrier coat additives used for electrostatic charging phenomenon.

(Comparative Example 3)
640 g of polymer particles were obtained in the same manner as in Example 1 except that 320 parts by weight of methyl methacrylate and 480 parts by weight of allyl methacrylate were used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate. It was.
The resulting polymer particles had an average particle size of 0.09 μm and a gel fraction of 99.8%. The storage modulus could not be measured because the specimen did not melt. Since the obtained polymer particles do not have specific thermal characteristics, they are unsuitable as external additives for electrophotographic toners and carrier coat additives used for electrostatic charging phenomenon.

(Comparative Example 4)
In the same manner as in Example 1, except that 760 parts by weight of methyl methacrylate and 40 parts by weight of ethylene glycol dimethacrylate (EGDMA) were used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate. 640 g of particles were obtained.
The resulting polymer particles had an average particle size of 0.12 μm, a gel fraction of 54.5%, and a storage elastic modulus of 1.0 × 10 ⁶ . The polymer particles have a low gel fraction and poor solvent resistance, and are unsuitable as external additives for electrophotographic toners and carrier coat additives used for electrostatic charging phenomenon.

(Comparative Example 5)
640 g of polymer particles were obtained in the same manner as in Example 1 except that 640 parts by weight of methyl methacrylate and 160 parts by weight of ethylene glycol dimethacrylate were used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate. Obtained.
The resulting polymer particles had an average particle size of 0.12 μm and a gel fraction of 86.4%. The storage modulus could not be measured because the specimen did not melt. Since the obtained polymer particles do not have specific thermal characteristics, they are unsuitable as external additives for electrophotographic toners and carrier coat additives used for electrostatic charging phenomenon.

(Comparative Example 6)
640 g of polymer particles in the same manner as in Example 1 except that 760 parts by weight of methyl methacrylate and 40 parts by weight of divinylbenzene (DVB) were used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate. Got.
The resulting polymer particles had an average particle size of 0.13 μm, a gel fraction of 1.4%, and a storage elastic modulus of 3.0 × 10 ⁶ . The obtained polymer particles have a low gel fraction and do not have specific thermal characteristics, and thus are not suitable as external additives and carrier coat additives for electrophotographic toners used for electrostatic charging phenomenon. .

(Comparative Example 7)
640 g of polymer particles were obtained in the same manner as in Example 1 except that 640 parts by weight of methyl methacrylate and 160 parts by weight of divinylbenzene were used instead of 760 parts by weight of methyl methacrylate and 40 parts by weight of allyl methacrylate. .
The obtained polymer particles had an average particle size of 0.14 μm and a gel fraction of 93.4%. The storage modulus could not be measured because the specimen did not melt. Since the obtained polymer particles do not have specific thermal characteristics, they are unsuitable as external additives for electrophotographic toners and carrier coat additives used for electrostatic charging phenomenon.

  The result of Examples 1-7 and Comparative Examples 1-6 is shown in Table 1 with the used raw material and those usage-amounts.

  From the results in Table 1, the polymer particles of the present invention (Examples 1 to 7) have a thermal property that can be appropriately fused by mechanical external force and heat while having a high gel fraction, and an electrostatic charge. It can be seen that it is suitable for an external additive for electrophotographic toner and a carrier coat additive used for an electric phenomenon.

Claims (4)

It is composed of a polymer derived from a polymerizable monomer containing 50 to 97% by weight of a (meth) acrylic acid ester monomer and 3 to 50% by weight of an asymmetric polyvinyl monomer having two or more vinyl groups having different reactivity,
The (meth) acrylate monomer is methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) T-butyl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate and At least one selected from stearyl (meth) acrylate,
The asymmetric polyvinyl monomer is allyl (meth) acrylate, and has an average particle size of 0.05 to 0.5 μm, a gel fraction of 60% or more, and 160 of 3 × 10 ⁴ to 2 × 10 ⁶ Pa or less. Polymer particles characterized by having a storage elastic modulus G 'at ° C. The polymer particle according to claim 1, wherein the polymerizable monomer contains 60 to 95% by weight of the (meth) acrylic acid ester monomer and 5 to 40% by weight of the asymmetric polyvinyl monomer. Claim 1 or electrophotographic external additive for toner comprising polymer particles according to 2. Carrier coating additive comprising a polymer particle according to claim 1 or 2.